197,327 research outputs found
Extension, refinement and validation of the Simple Lateral Mechanism Analysis (SLaMA) for the seismic assessment of RC structures
No full textIl lavoro in questa tesi riguarda l’estensione, il miglioramento e la validazione della metodologia Simple Lateral Mechanism Analysis (SLaMA) per la valutazione sismica di strutture in CA. Raccomandato nelle linee guida neozelandesi del 2017 relative alla valutazione sismica, NZSEE (2017), SLaMA é un metodo di analisi non-lineare che permette di avere una stima della capacitá di strutture esistenti ed é valido per telai, pareti o sistemi misti telaio/parete. L’idea di base é procedere “dal locale al globale”, partendo dal comportamento di componenti singoli, estendendolo a specifici sottoschemi ed infine giungendo al comportamento globale dell’edificio. É anche possibile considerare gli effetti torsionali in campo non-lineare. Dato che il metodo si basa su ipotesi semplificate, non é necessario ricorrere a modelli numerici e i calcoli possono essere fatti “a mano (i.e. utilizzando un foglio elettronico). La prima parte di questo lavoro di ricerca riguarda i sistemi a telaio nudo, identificando aree di miglioramento della procedura SLaMA esistente e proponendo una procedura estesa e migliorata. Essa é stata validata attraverso la sua applicazione a 40 casi studio ideali e il confronto con i risultati di analisi numeriche raffinate (FEM Pushover). I risultati indicano che la procedura SLaMA modificata permette di identificare accuratamente il meccanismo plastico del telaio, considerando l’effettiva gerarchia delle resistenze dei suoi componenti, e di calcolarne la curva di capacitá con errori accettabili per i suoi parametri più significativi. La parte successiva del lavoro riguarda lo sviluppo di una nuova procedura SLaMA, non presente in NZSEE (2017), per sistemi a telaio tamponato, che rappresentano una cospicua parte del patrimonio edilizio, soprattutto in Europa. La nuova metodologia si basa su una procedura meccanica, proposta in questo lavoro, per disaccoppiare i contributi al taglio alla base relativi al telaio e alle tamponature, per un qualunque valore dello spostamento globale. La procedura di disaggregazione é applicabile a prescindere dalla distribuzione delle tamponature e della curva caratteristica dei puntoni equivalenti. Puó essere inoltre applicata per la post-processione dei risultati di analisi Pushover o Time History di telai tamponati. In analogia a quanto fatto per i telai nudi la procedura SLaMA é stata validata tramite confronto con i risultati di analisi Pushover per 72 casi studio. Sono stati inoltre considerati i sistemi resistenti misti telaio/parete con l’obiettivo di proporre una nuova procedura SLaMA che considerasse esplicitamente l’interazione tra la parte a telaio con quella a parete, includendo il calcolo delle forze da essi scambiate e le eventuali coppie concentrate dovute alla presenza di travi di collegamento. Con la nuova procedura SLaMA é possibile stimare il comportamento dei sistemi duali con grande accuratezza, come dimostrato da una vasta analisi parametrica (SLaMA vs Pushover) che coinvolge 24 casi studio. L’ultima parte del lavoro riguarda la valutazione sismica di un edificio realmente esistito e che ha subito notevoli danni durante la sequenza sismica di Christchurch (Nuova Zelanda) tra il 2010 e il 2011. Lo “score sismico” (capacitá fratto domanda) é stato indipendentemente valutato con diversi metodi di analisi: Lineare Statica, Lineare Dinamica, Non-Lineare Statica (Pushover e SLaMA), Non-Lineare Dinamica. In primis questo confronto incrociato dimostra l’affidabilitá del metodo SLaMA nella valutazione di casi reali complessi. Questo studio dimostra inoltre come le informazioni ottenute utilizzando SLaMA possano essere efficacemente usate per calibrare i parametri fondamentali necessari per gli altri metodi di analisi, o interpretarne i risultati. Sebbene alcuni passi della procedura possono essere calibrati in maniera piú raffinata grazie a sviluppi futuri si puó sicuramente affermare che SLaMA sia un metodo di analisi robusto. Esso é in grado di fornire al tecnico valutatore gli strumenti per comprendere i dettagli del comportamento di un edificio usando esclusivamente calcoli fatti a mano (eventualmente implementati in un semplice foglio elettronico).This dissertation is focused on the extension, refinement and validation of the Simple Lateral Mechanism Analysis (SLaMA) method for the seismic assessment of RC buildings. Suggested in the 2017 New Zealand guidelines for seismic assessment, NZSEE (2017), SLaMA is an analytical non-linear analysis technique that provides a first estimation of the global capacity curve of the primary lateral-resisting systems in RC buildings, including bare frames, cantilever walls and dual wall/frame systems. The basic idea is to progress “from local to global”, extending the local behaviour of the structural members to selected sub-schemes, and finally to the global non-linear response of the building. Inelastic torsional effects are also included. Since simplified assumptions are made, no numerical computer model is needed and hence all the calculations can be performed “by hand” (i.e. implemented in an electronic spreadsheet). The first part of this investigation is related to bare frame Lateral Resisting Systems, with the identification of potential areas of improvement for the existing SLaMA procedure and the proposal of an extended/refined one. The refined procedure for bare frames is validated through the application to a set of 40 ideal case studies and the comparison with refined numerical analyses (FEM Pushover). The results show that the refined SLaMA procedure allows to accurately identify the expected plastic mechanism of the frame, also considering the actual hierarchy of strength of its members, and to properly estimate its non-linear capacity curve with acceptable errors on the most meaningful parameters. The subsequent part of the investigation involves the development of a novel SLaMA method to evaluate the capacity curve of masonry-infilled frames systems, which represent a large portion of the building portfolio, especially in Europe. The incorporation of the contribution of the infills is completely absent in the NZSEE (2017) SLaMA framework. The methodology is based on a proposed mechanically-based procedure to decouple the frame and infills contributions to the overturning moment (and hence base shear) capacity for any value of the global displacement. The decoupling procedure is applicable regardless of the distribution of the infills and of the non-linear Axial load-Axial strain of the equivalent struts. It can be applied to post-process the results of Pushover or Time History analyses of different types of infilled frames (material-wise). Similarly to what done for bare frames, an extensive SLaMA vs numerical Pushover comparison, for a set of 72 ideal case studies, is used to validate the proposed SLaMA procedure. Part of the investigation is dedicated to dual wall/frame system structures, proposing a novel SLaMA procedure in which the coupled behaviour of the frame and wall(s) components is expressly considered, including the calculation of the exchanged forces and the concentrated moment couples due to the possible presence of link beams. By using the new SLaMA procedure it is possible to capture the non-linear behaviour of the dual system with extreme accuracy, as demonstrated with an extensive SLaMA vs numerical Pushover parametric analysis comprising 24 ideal case studies. The last step of the work is the seismic assessment of a real case study building, severely damage in the Christchurch (New Zealand) sequence of earthquakes in 2010-2011. Different analysis techniques are used to independently derive the “seismic score” of the building (capacity over demand), including: Linear Static, Linear Dynamic, Non-Linear Static (numerical Pushover and SLaMA) and Non-Linear Dynamic analyses. Firstly, this demonstrates the reliability of the SLaMA method in assessing real, complex cases by means of a cross-validation. Moreover, and perhaps more importantly, it is deemed that this comparative study demonstrates how the insights gained by using SLaMA can be used to calibrate important parameters needed when adopting other analysis techniques, or interpreting their results. Additional investigations might help in fine-tuning some of its steps but, overall, it is deemed that SLaMA constitutes a robust analysis technique that allows the assessor to really understand the behaviour of an RC building only using hand calculations, possibly implemented in a simple spreadsheet
Seismic assessment of a RC case study building using the Simple Lateral Mechanism Analysis, SLaMA, method
No full textThe seismic assessment of an existing structure is a complex procedure. In
the
eval-
uation
of
the structural capacity
,
difficulties arise in the definition of the lateral resisting mem-
bers,
in
the estimation of
the
lateral capacity
from component
to
system level
.
T
he
identification
of the local and global mechanism
s
,
depending on the
hierarchy of strength
at subassembly
level, is
a
challenging
task
. Nowadays,
advanced
numerical
analys
i
s
procedures
, implemented
in user
-
friendly commercial software, are commonly adopted in the current practice to over-
come the difficulties in the use of non
-
linear
analyses
.
Ne
vertheless, their accuracy strongly
depends on the ability of the numerical model to capture all the probable failure mechanisms.
To help the user
in the assessment of the probable failure mechanism and to have a first esti-
mation of the building lateral ca
pacity,
the Simple Lateral Mechanism Analysis (SLaMA)
method
has been recently developed and included in the
NZSEE
2016
guidelines. SLaMA is a
simple
and reliable
“by
-
hand”
tool to derive the local and global mechanism of a structural
system and the corresponding capacity curve.
T
his paper
deals with the application of the
SLaMA to
an existing
RC
building severely damaged during the Christchurch earthquake (2011
,
New Zealand
)
.
The lateral capacity of f
our 2D resisting systems
was
assessed following the
SLaMA
method
.
The
results of a refined nonlinear numerical model were used to assess the
accuracy and reliability of
SLaMA.
The good match confirmed that SLaMA can be a useful
and simple
tool to have a first estimation of the building lateral response
. It allows to identify
the main structural weaknesses driving the user to the development of
more refined nonlinear
model
SIMPLE LATERAL MECHANISM ANALYSIS (SLaMA) FOR THE SEISMIC ASSESSMENT OF UNREINFORCED MASONRY STRUCTURES
No full textOf the broad range of displacement-based assessment methods available to structural engineers, one that has seen recent uptake on a design code level is the Simple Lateral Mechanism Analysis (SLaMA). In particular, the 2017 New Zealand Technical Guidelines for (seismic) Engineering Assessments and the Dutch practice note NPR9998:2018 both enable the use of SLaMA for the seismic assessment of unreinforced masonry structures. This paper investigates the merits and drawbacks of SLaMA as a seismic assessment method for unreinforced masonry structures based on practical experience in New Zealand and the Netherlands.
In general, the SLaMA method focuses on calculating the force and displacement capacities of individual structural elements and then identifying a global failure mechanism. The global displacement capacity of the structural system is then evaluated against the displacement demand on an equivalent single-degree-of-freedom system. This approach can easily be facilitated by hand or spreadsheet-based calculation and alleviates the need to develop a numerical model, which can often be complex for masonry structures. Consequently, SLaMA is generally found to be a cost-effective assessment methodology. This is well suited to masonry structures, which, due to their typically historic nature and limitations of the construction material, are often low-rise structures with relatively lower asset values.
Following an overview of the SLaMA methodology, its specific application to masonry structures is discussed and a number of key considerations identified. It is then shown that there are a number of merits and drawbacks in utilizing SLaMA for the assessment of masonry structures. The paper also provides an example application of SLaMA to a typical Dutch unreinforced masonry terraced house. This example helps to elucidate the peculiarities of masonry structures and some of the technical challenges the engineer might face. Furthermore, the example demonstrates that SLaMA is very efficient when applied to relatively simple masonry buildings and when a reasonable set of starting assumptions are used
Seismic assessment of a RC case study building using the simple lateral mechanism analysis, SLaMA, method
No full textThe seismic assessment of an existing structure is a complex procedure. In the evaluation of the structural capacity, difficulties arise in the definition of the lateral resisting members, in the estimation of the lateral capacity from component to system level. The identification of the local and global mechanisms, depending on the hierarchy of strength at subassembly level, is a challenging task. Nowadays, advanced numerical analysis procedures, implemented in user-friendly commercial software, are commonly adopted in the current practice to overcome the difficulties in the use of non-linear analyses. Nevertheless, their accuracy strongly depends on the ability of the numerical model to capture all the probable failure mechanisms. To help the user in the assessment of the probable failure mechanism and to have a first estimation of the building lateral capacity, the Simple Lateral Mechanism Analysis (SLaMA) method has been recently developed and included in the NZSEE 2016 guidelines. SLaMA is a simple and reliable "by-hand" tool to derive the local and global mechanism of a structural system and the corresponding capacity curve. This paper deals with the application of the SLaMA to an existing RC building severely damaged during the Christchurch earthquake (2011, New Zealand). The lateral capacity of four 2D resisting systems was assessed following the SLaMA method. The results of a refined nonlinear numerical model were used to assess the accuracy and reliability of SLaMA. The good match confirmed that SLaMA can be a useful and simple tool to have a first estimation of the building lateral response. It allows to identify the main structural weaknesses driving the user to the development of more refined nonlinear models
A slama-based analytical procedure for the cost/performance-based evaluation of buildings
No full textThe decision-making process for seismic risk is affected by the assessment/design procedure adopted and rigorous methodologies have been developed to estimate performance metrics relevant to stakeholders to take informed decisions. Input data for loss estimations of buildings are typically floor accelerations and inter-storey drift ratios, generally obtained from: 1) simplified evaluations, based on linear models and static analysis, 2) more accurate non-linear static analyses, or 3) more complex and time-consuming non-linear history analyses. Considering that non-linear static analyses are arguably the best compromise between accuracy and simplicity, this paper proposes the application of an analytical non-linear static procedure, based on the Simplified Lateral Mechanism Analysis (SLaMA) of the NZSEE 2017 Guidelines, for the cost/performance-based evaluation of Reinforced Concrete structures. In order to validate the accuracy of the method, multi-storey case-study buildings are analyzed using different structural analysis methods (the proposed SLaMA-based approach vs. numerical Pushover vs. Time-History) and through sophisticated or simplified loss assessment methodologies (FEMA P-58, 2012; D.M. n.65, 2017). The results in terms of Expected Annual Losses from the SLaMA-based approach are quite satisfactory - increase of 7-18% or 3-7% compared to numerical Pushover results from probabilistic or simplified loss estimations, increase of 20-40% compared to numerical Time-History results - and, in general, more accurate than static analyses results, even though no numerical modelling is needed. Therefore, the SLaMA-based method can be a promising tool for a daily use of practicing engineers for a rapid evaluation of economic losses for both the seismic assessment of existing buildings and the initial feasibility studies of new structures
Implementation and Validation of the Simple Lateral Mechanism Analysis (SLaMA) for the Seismic Performance Assessment of a Damaged Case Study Building
No full textThe new guidelines for the seismic assessment of existing buildings recently introduced by the New Zealand Society for Earthquake Engineering (NZSEE) recommend the Simple Lateral Mechanism Analysis (SLaMA) as an “analytical” first phase of any other numerically-based analysis. This article illustrates the development of the SLaMA method and its validation with reference to an existing RC building severely damaged during the Christchurch earthquake (2011). The capacity of the lateral resisting systems is assessed from component/subassembly to system level. The comparison of the results with observed damage and with the outcomes of refined numerical analyses confirms the effectiveness of this metho
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
Implementation and Validation of the Simple Lateral Mechanism Analysis (SLaMA) for the Seismic Performance Assessment of a Damaged Case Study Building
No full textThe new guidelines for the seismic assessment of existing buildings recently introduced by the New Zealand Society for Earthquake Engineering (NZSEE) recommend the Simple Lateral Mechanism Analysis (SLaMA) as an “analytical” first phase of any other numerically-based analysis. This article illustrates the development of the SLaMA method and its validation with reference to an existing RC building severely damaged during the Christchurch earthquake (2011). The capacity of the lateral resisting systems is assessed from component/subassembly to system level. The comparison of the results with observed damage and with the outcomes of refined numerical analyses confirms the effectiveness of this method
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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